Learn how this tool can help you understand and manage your glucose levels effectively.
As use of continuous glucose monitors has become more common, people with diabetes have started using a measurement known as the GMI.
Your GMI is the average (mean) glucose value based on the data collected by your CGM. Here’s how to get your GMI:
The GMI formula
You need the average glucose values from your CGM to get the GMI percentage:
GMI (%) = 3.31 + 0.02392 x [mean glucose in mg/dL].
For example, if your mean glucose level was 150 mg/dL, your GMI would be 6.9% ( 51.9 mmol/mol ).
The GMI is not the same as the A1C.
In 2018, a team of researchers found that GMI was a better indicator of someone’s estimated glucose trends over time.
Although their study found that 51% of people only saw an approximate 3% difference between their GMI and laboratory A1C results, it’s still important to remember that they’re calculated differently. You’re using the mean glucose values from your CGM to determine the GMI rather than measuring how much sugar is attached to your red blood cells.
If your GMI is always lower than your A1C, your doctor will want to make sure you adjust your target goals accordingly. You might also need to be more vigilant about minimizing the possibility of hypoglycemia.
The study suggested that if your GMI is always higher than your A1C, you should set your laboratory A1C target goal slightly lower to reduce the risk of excessive hyperglycemia.
This table can help you understand more about GMI:
| CGM-derived average glucose (mg/dL) | GMI (%) |
|---|---|
| 100 | 5.7 |
| 125 | 6.3 |
| 150 | 6.9 |
| 175 | 7.5 |
| 200 | 8.1 |
| 225 | 8.7 |
| 250 | 9.3 |
| 300 | 10.5 |
| 350 | 11.7 |
Remember, though: GMI numbers are not the same as A1C and shouldn’t be compared without first discussing the results with your endocrinologist or diabetes care team.
Most importantly, any diabetes number — whether it’s a single glucose reading, a pattern on Time in Range, A1C result, or GMI measurement — is only a piece of information used in managing your diabetes. A number or result doesn’t define you.
With advances in technology, you now have more options to help you keep track of your blood sugar levels.
CGM technology can help you learn more about your blood sugar levels, including the immediate impact of the choices that you make and how well you keep your blood glucose levels in your target range over time.
Using both A1C and GMI gives you the information you need to maintain better control over your blood sugar levels and to stay as healthy as possible.